The invention relates to inclination measurement apparatus, and more particularly to an inclination measurement apparatus capable of highly accurate measurements to an accuracy in the order of 10xe2x88x925xc2x0.
Inclination measurement apparatus for highly sensitive applications including inter alia the setting up of and subsequent inclination monitoring of antennas, artillery, radar, telescopes, and the like, requiring ultra accurate inclination measurements may suffer from transient and aging biases leading to errors in the same order as the desired accuracy, or even greater. Inclination measurement apparatus are illustrated and described in U.S. Pat. Nos. 3,829,9871, 3,849,897, RE 28,694, 4,528,760, 4,866,850, 5,210,954, and 5,317,810, and one known approach to negate transient biases arising from ambient temperature changes is to install inclination measurement apparatus within a so-called thermal blanket.
In accordance with the present invention, there is provided an inclination measurement apparatus for measuring the inclination of a surface to the horizontal, the apparatus comprising:
a) a base plate for mounting the apparatus on the surface;
b) a ball bearing including:
i. a housing washer rigidly mounted on said base plate, and having a flat upper bearing surface,
ii. a ball and cage thrust assembly set on said upper bearing surface, and
iii. a shaft washer having a flat lower bearing surface set on said ball and cage thrust assembly, and being rotatable thereon between a first pair of diametrically opposite orientations defining a first measurement axis on the horizontal to the local gravity vector prevailing at the location of the apparatus; and
(c) a first clinometer mounted on said shaft washer for obtaining an inclination measurement at each of said pair of diametrically opposite orientations whereby the true inclination of the surface relative to the horizontal along said measurement axis is determinable from the difference between said pair of measurement inclinations.
By virtue of high manufacturing tolerances of its upper and lower bearing surfaces and its balls, the ball bearing demonstrates a high degree of parallelism between its lower and upper bearing surfaces, thereby facilitating the measuring of an inclination to the horizontal to an accuracy in the order of about 10xe2x88x925xc2x0. In addition, the inclination measurement apparatus of the present invention is readily manufacturable both in terms of its relative small number of parts, and the ease of their assembly, and is particularly suitable for applications for which the degree of accuracy required increases the smaller the inclination relative to the horizontal to be measured.